Jet dispersing device have been used for in-line mixing less miscible coating material ingredients such as aqueous 2-component polyurethane type coating materials comprising a main agent and a curing agent to each other.
[Patent Document 1] JP-A No. 7-331170
FIG. 4 shows such an existent jet dispersing device 51 in which a partition wall 54 for partitioning a flow inlet 53in and a flow outlet 53out in a tubular housing 52.
The partition wall 54 is formed by extending a bottomed cylindrical tubular member 56 from a central opening to the flow inlet 53in of a flat plate-flange 55, and fine nozzle holes 57 each with a diameter of about 0.5 mm are formed and opposed in the circumferential surface of the tubular wall 56a. 
FIG. 5 shows a coating material supply system 61 in which the jet dispersing device 51 is disposed in an in-line arrangement. After storing a main agent and a curing agent supplied from a main agent supply source 62A and a curing agent supply source 62B in high pressure cylinders 63A, 63B, when they are supplied under high pressure at a flow rate in accordance with the mixing ratio to the jet dispersing device 51, the main agent and the curing agent merged on the side of the flow inlet 53in of the jet dispersing device 51 are jetted to the down stream upon passage through the nozzle holes 57 toward the flow outlet 53out and they are dispersed as fine particles respectively and mixed under emulsification.
Accordingly, when the mixed coating material is supplied to a coating machine 64, the main agent and the curing agent which are difficult to be mixed can be coated in a state being mixed uniformly.
Then, in the coating material supply system 61 as described above, it is necessary that the coating material flow channel 65 downstream of the meeting place for the main agent and the curing agent has to be cleaned frequently in order to prevent a residual coating material from curing.
However, even when a cleaning fluid such as a cleaning liquid or cleaning air is supplied under pressure from the flow inlet 53in to the flow outlet 53out of the jet dispersing device 51, since fine nozzle holes 57 formed in the partition wall 54 gives a flow channel resistance to lower the flow speed of the cleaning fluid, it requires a long time for cleaning and increase the amount of the cleaning liquid and the cleaning air, to bring about a problem that efficient cleaning is impossible.
While it has been attempted to increase the pressure of supplying the cleaning liquid and the cleaning air to thereby shorten the cleaning time, this not only requires a high pressure pump for supplying the cleaning liquid and the cleaning air but also complicates the facility such as by the use of hoses and connectors acceptable for pressure proofness and, on the other hand, the cleaning time can not be shortened by so much.